ampere per meter squared

The ampere per meter squared, symbolized A/m ² , is the International Unit of electric current density . A current density of 1 A/m ² represents one ampere of electric current flowing through a material with a cross-sectional area of one square meter.

The ampere per meter squared is a small unit of current density. Suppose a wire has a cross-sectional area of one millimeter squared (1 mm ² ). This is 0.000001 meter squared (10 ^-6 m ² ). If the current density in this wire is 1 A/m ² , then the wire carries 10 ^-6 A, or one microampere (1 µA), a tiny current. Suppose this same wire carries a current of one ampere (1 A), which is an entirely plausible scenario. Then the current density in the wire is 1,000,000 amperes per meter squared (10 ⁶ A/m ² ).

Sometimes, larger units of current density are specified. For example, one ampere per millimeter squared (A/mm ² ) represents a current of 1 A flowing through a conductor with a cross-sectional area of 1 mm. This unit is equal to 1,000,000 (10 ⁶ ) A/m ² . One milliampere per millimeter squared (mA/mm ² ) represents a current of 1 mA flowing through a conductor with a cross-sectional area of 1 mm. This unit is equal to 1,000 (10 ³ ) A/m ² .

Determination of current density is straightforward in direct-current ( DC ) and low-frequency alternating-current ( AC ) circuits, because the current is distributed uniformly throughout the cross section of a solid conductor. But at radio frequencies ( RF ), more current flows near the outer surface of a solid conductor than near its center. This is known as skin effect , and it dramatically reduces the conductivity of wires in RF applications as compared with DC and low-frequency AC circuits. At RF, current density is sometimes near zero near the center of a solid conductor, and quite high near the outer periphery. The average current density can nevertheless be calculated according to the following formula:

D = I / X

where D is the current density in amperes per meter squared, I is the current in amperes, and X is the cross-sectional area of the conductor in meters squared.

Also see ampere , meter squared , skin effect , and International System of Units ( SI ).

Last updated on: Sep 21, 2005

>  Enterprise Software related Research & News >  White Papers for the Retail Industry Are you a Know-IT-All? What handy input device did Douglas Englebart invent? Answer  Get the Word of the Day  Follow us on Twitter WORD OF THE DAY... SAP LEARN MORE ABOUT... SAP trends USA Contributors Worldwide Contributors Awards and Recognition Our 60+ tech-specific sites WhatIs.com RSS Feeds